Cardiac CTA

Acute chest pain is the most common diagnosis in the emergency department that requires expeditious and meticulous diagnostic testing and clinical decision-making.1 A diagnosis of chest pain can be challenging to exclude even after careful assessment and evaluation. As a result, patients often are needlessly admitted until the diagnosis of acute coronary syndrome can be excluded. Admitting these patients causes a significant financial burden on hospitals by increasing hospital bed occupancy rates and gratuitous diagnostic tests. This article will explore how a cardiac computed tomography angiography (CTA) enables accurate and safe evaluation of significant coronary artery disease in patients with acute chest pain.

 

Cardiac CTA
There are two types of cardiac computed axial tomography (CAT) scans: A coronary calcium score and a cardiac CTA. A cardiac CTA utilizes advanced CAT scan technology, along with IV contrast, beta blockers, and nitroglycerin that results in a high-resolution 3D imaging of the heart and coronary arteries. The combination of the high resolution 3D images and use of the medications helps physicians visualize and assess if blockages or plaque is present in the coronaries and to what extent or severe the blockage is.2 These results will either direct care to a cardiac catherization, if cardiac stents are needed or treat the patient medically, if any treatment is needed at all. Whereas, calcium score test on the contrary simply employs CAT scan technology to visualize any plaque in the coronary arteries.

The difference between the two tests is the use of IV contrast, beta blockers, and nitroglycerin utilized by a cardiac CTA. A calcium score test unlike the cardiac CTA does not utilize these medications to produce high resolution 3D images. However, the calcium score test can be performed within five minutes, whereas a cardiac CTA can take 30 minutes to perform. And although the cardiac CTA is not a substitute for a cardiac catheterization, it can be performed faster than a catherization and offers less risk of discomfort and infections with decreased recovery time.

 

What to Expect
For the calcium score test, patients are scanned for a few minutes to assess coronary arteries for plaque, whereas the coronary CTA is more involved. A nurse will perform a physical assessment and assess the patient’s cardiac history. Afterward, a pulse oximetry and blood pressure cuff is placed. Physicians prefer the heart rate to be 60 and below to visualize the coronary arteries more effectively. If the heart rate is above 60, a beta blocker is administered.

Once the heart rate is 60 or below, the patient is placed on the table, and electrodes are placed along with an IV. Once this is completed, the table will move in and out of the scanner. The calcium scan is performed during the first five minutes of the cardiac CTA. Once the calcium score is completed, the scanner will proceed to visualize the coronaries and heart chambers. During the scan, IV dye is administered to illuminate the arteries along with the administration of nitroglycerin to dilate the arteries. The scan itself takes a total of 30 minutes. After the scan is complete, the nurse will assess the patient’s heart rate and blood pressure. Once the blood pressure and heart rate are similar to their entry, then the discharge papers are given. Normally, patients are able to drive themselves home and resume normal activities.3

 

Indications
When it comes to predicting the risk of future cardiac events, physicians consider patients risk factors such as, family history, age, etc, but the healthcare community is finding that the most reliable indicator for cardiac death is plaque.4 The findings from the scan are expressed as a calcium score that estimates the extent of coronary disease. The amount of plaque has been recognized as a powerful independent predictor of future heart problems.4 Candidates for this study include patients with a history of hyperlipidema, family history of heart attacks, or simply wanting to be weaned off statin medications.

Coronary CTA scan is useful in the evaluation of patients who are low risk to assess for blockages. Low risk candidates include patients with risk factors such as family history, inconclusive stress test results, experiencing unusual symptoms for coronary artery disease including atypical chest pain, or complaints of increasingly shortness of breath. Patients who need evaluation of their cardiomyopathy or any cardiac mass may benefit. High risk patients are not candidates and include those with a history of cardiac surgery, “typical” chest pain, and patients with atrial arrhythmias, sensitivity to beta blockers, pacemakers or renal insuffiency.5

The gold standard test for diagnosing and treating plaque deposits is still the invasive angiography or cardiac catheterizations.6 A cardiac catheterization is where a slender tube will be threaded into the heart through the femoral or radial artery. Angioplasty can push the plaque against the artery walls allowing blood, oxygen, and nutrients to flow. However, this procedure is costly, time-consuming, and can have vascular complications, whereas a cardiac CTA, is a noninvasive tool to identify plaque that may contribute to a coronary event.2

Acute chest pain is the most common complaint in the ED and appropriate triage is a must.1 Cardiac CTA’s are especially useful when cardiac enzymes and electrocardiograms results are normal. Predictive long-term prognosis and cost effectiveness has been confirmed by a number of studies when a CTA is utilized.1 Since the introduction of the 64 slice scanners in 2005, cardiac CTA’s have become instrumental in triaging patients with chest pain.6 It is a promising, noninvasive tool for low-risk patients. The following are summaries of studies demonstrating the high sensitivity and specificity in detecting arterial stenosis that a cardiac CTA can display.

 

Studies
Rubinshtein and Halon conducted a prospective study that included 58 ED patients with acute chest pain.7 These patients underwent a cardiac CTA to diagnosis and exclude acute coronary syndrome. Fifteen months after their cardiac CTA, the investigators evaluated the clinical outcomes of these patients and found no deaths, myocardial infarctions, or other cardiac events occurred in the 35 patients discharged from the ED after a normal or negative cardiac CTA diagnosis. The remaining 23 patients needed surgical intervention following cardiac CTA.

Hollander, Chang, and Shofer prospectively evaluated 586 low to intermediate risk patients who underwent a cardiac CTA in the ED for evaluation of acute chest pain.8 This sample included patients with atypical chest pain, no family history, or sensitivity to beta blockers and a normal creatnine level. Interestingly, patients discharged from the ED with a negative CTA (n= 476 or 84%) had a very low event rate (2%) of a cardiac complication post discharge.

Meigjbourn, Meijs, and Schuijf addressed if a CTA was able to detect or rule out coronary artery disease in 360 patients with symptomatic acute and stable angina. The results yielded specificity and sensitivity of 97% and 99%, in predicting the presence of coronary stenosis.9 These studies demonstrate the accurate and safe evaluation of significant coronary artery disease. Importantly, a negative CTA predicts a low rate of adverse cardiovascular events.

 

SEE ALSO: Earn CE: Cardiac Complications in Long-Term Care

Cost-Effectiveness
White cited that approximately 15% of patients presenting in the ED with chest pain are experiencing chest pain, while approximately 50% of ED patients have benign causes for their chest pain.10 The abundance of caution and the reason for the admissions is the risk of legal consequences. Cost-effectiveness is another factor when considering the merits of a CTA.

Hendel and Dahdah compared the standard of care approach, which included an electrocardiogram, biomarkers, and stress test to the use of a cardiac CTA for low risk patients.6 In this study, low-risk patients included those experiencing atypical chest pains or denied familial cardiac history. Results yielded that a cardiac CTA provided a more efficient and quicker diagnosis, 3.4 hours versus 15 hours, and significantly reduced hospital costs $1,586 versus $1,872.6

Rajani, Brum, Preston, Carr-White, and Berman evaluated the results of early intervention of a coronary CTA in 23 patients hospitalized with chest pain, and observed a mean reduction in cost of $8,448 and a reduction in hospital stay of 1.3 days when compared with a match control population receiving the standard care or biomarkers and stress test.11

A similar study conducted by Chow and Yam included 53 patients with chest pain and included a coronary CTA as part of the cardiac work up during their hospital stay. When comparing the experimental group with control group, the mean length of hospital stay was significantly reduced 25.4 to 14.3 days and cost per patient was reduced from $7,597 to $6,153 when comparing the experimental group to the control group.12

Goldstein, Gallagher, and O’Neil randomized 197 low risk patients presenting in the ED with chest pain to receive either a CTA or stress test.13 The CTA group showed the time to diagnosis was reduced by 11.6 hours, the cost reduced by $286, and the number of repeat evaluations for chest pain reduced by 7% from 9% from the standard group. As demonstrated, the utilization of cardiac CTA’s has shown to decrease time and money when compared to the routine standard of care. Another benefit of a cardiac CTA is the ability to impact or aid in the clinical management in patients presenting with acute chest pain.

 

Nursing Implications
It is pertinent for the nurse to risk stratify the appropriate patients to undergo a cardiac CTA through a detailed history and physical for appropriate patient selection. Once the patient is selected, it is essential to check the patient’s renal function, since IV contrast will be given. Before the patient is scanned, the nurse must explain the rationale for monitoring of the pulse and blood pressure, as well as the need for beta blocker medication. If a beta blocker is required, the healthcare provider must explain the medication side effects, mechanism of action, and indication for usage.

When the patient is placed on the scanning table, nurses must provide comfort. Once the patient is placed on the table and the IV line is placed, the nurse must assess for patency to help avoid the possibility of an extravasation. Finally, it is essential to inform the patient to drink plenty of fluids, preferable water after the scan to flush out the IV contrast out of the kidneys to and avoid the risk of kidney injury.

Chest pain requires immediate and diligent assessment, diagnostic testing, and clinical decision making for adequate diagnosis since a myriad of non coronary etiologies may masquerade as chest pain.10

Traditionally, diagnosis includes the standard electrocardiogram test, cardiac biomarkers, stress tests, and possible cardiac catheterizations. However, the issue with these diagnostic tests is that some results may be normal or inconclusive making a delayed or missed diagnosis that can cause a substantial number of morbidity and mortality among this patient population.1

 

References for this article can be accessed online at www.advanceweb.com/nurses. Click on Resources, then References.

 

Felice Hefferan has been a staff nurse in the cardiac rehab unit for nine years at Main Line Health in eastern Pennsylvania. Shannon Rutberg is a clinical nurse educator at Bryn Mawr Hospital, part of Main Line Health.

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